types of fetal presentation ultrasound

Variation in fetal presentation

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Delivery presentations
Variation in delivary presentation
Abnormal fetal presentations

There can be many variations in the fetal presentation which is determined by which part of the fetus is projecting towards the internal cervical os . This includes:

cephalic presentation : fetal head presenting towards the internal cervical os, considered normal and occurs in the vast majority of births (~97%); this can have many variations which include

left occipito-anterior (LOA)

left occipito-posterior (LOP)

left occipito-transverse (LOT)

right occipito-anterior (ROA)

right occipito-posterior (ROP)

right occipito-transverse (ROT)

straight occipito-anterior

straight occipito-posterior

breech presentation : fetal rump presenting towards the internal cervical os, this has three main types

frank breech presentation (50-70% of all breech presentation): hips flexed, knees extended (pike position)

complete breech presentation (5-10%): hips flexed, knees flexed (cannonball position)

footling presentation or incomplete (10-30%): one or both hips extended, foot presenting

other, e.g one leg flexed and one leg extended

shoulder presentation

cord presentation : umbilical cord presenting towards the internal cervical os

1. Fox AJ, Chapman MG. Longitudinal ultrasound assessment of fetal presentation: a review of 1010 consecutive cases. Aust N Z J Obstet Gynaecol. 2006;46 (4): 341-4. doi:10.1111/j.1479-828X.2006.00603.x - Pubmed citation
2. Merz E, Bahlmann F. Ultrasound in obstetrics and gynecology. Thieme Medical Publishers. (2005) ISBN:1588901475. Read it at Google Books - Find it at Amazon

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Pregnancy week by week
Fetal presentation before birth

The way a baby is positioned in the uterus just before birth can have a big effect on labor and delivery. This positioning is called fetal presentation.

Babies twist, stretch and tumble quite a bit during pregnancy. Before labor starts, however, they usually come to rest in a way that allows them to be delivered through the birth canal headfirst. This position is called cephalic presentation. But there are other ways a baby may settle just before labor begins.

Following are some of the possible ways a baby may be positioned at the end of pregnancy.

Head down, face down

When a baby is head down, face down, the medical term for it is the cephalic occiput anterior position. This the most common position for a baby to be born in. With the face down and turned slightly to the side, the smallest part of the baby's head leads the way through the birth canal. It is the easiest way for a baby to be born.

Head down, face up

When a baby is head down, face up, the medical term for it is the cephalic occiput posterior position. In this position, it might be harder for a baby's head to go under the pubic bone during delivery. That can make labor take longer.

Most babies who begin labor in this position eventually turn to be face down. If that doesn't happen, and the second stage of labor is taking a long time, a member of the health care team may reach through the vagina to help the baby turn. This is called manual rotation.

In some cases, a baby can be born in the head-down, face-up position. Use of forceps or a vacuum device to help with delivery is more common when a baby is in this position than in the head-down, face-down position. In some cases, a C-section delivery may be needed.

Illustration of the head-down, face-up position

Frank breech

When a baby's feet or buttocks are in place to come out first during birth, it's called a breech presentation. This happens in about 3% to 4% of babies close to the time of birth. The baby shown below is in a frank breech presentation. That's when the knees aren't bent, and the feet are close to the baby's head. This is the most common type of breech presentation.

If you are more than 36 weeks into your pregnancy and your baby is in a frank breech presentation, your health care professional may try to move the baby into a head-down position. This is done using a procedure called external cephalic version. It involves one or two members of the health care team putting pressure on your belly with their hands to get the baby to roll into a head-down position.

If the procedure isn't successful, or if the baby moves back into a breech position, talk with a member of your health care team about the choices you have for delivery. Most babies in a frank breech position are born by planned C-section.

Illustration of the frank breech position

Complete and incomplete breech

A complete breech presentation, as shown below, is when the baby has both knees bent and both legs pulled close to the body. In an incomplete breech, one or both of the legs are not pulled close to the body, and one or both of the feet or knees are below the baby's buttocks. If a baby is in either of these positions, you might feel kicking in the lower part of your belly.

If you are more than 36 weeks into your pregnancy and your baby is in a complete or incomplete breech presentation, your health care professional may try to move the baby into a head-down position. This is done using a procedure called external cephalic version. It involves one or two members of the health care team putting pressure on your belly with their hands to get the baby to roll into a head-down position.

If the procedure isn't successful, or if the baby moves back into a breech position, talk with a member of your health care team about the choices you have for delivery. Many babies in a complete or incomplete breech position are born by planned C-section.

Illustration of a complete breech presentation

When a baby is sideways — lying horizontal across the uterus, rather than vertical — it's called a transverse lie. In this position, the baby's back might be:

Down, with the back facing the birth canal.
Sideways, with one shoulder pointing toward the birth canal.
Up, with the hands and feet facing the birth canal.

Although many babies are sideways early in pregnancy, few stay this way when labor begins.

If your baby is in a transverse lie during week 37 of your pregnancy, your health care professional may try to move the baby into a head-down position. This is done using a procedure called external cephalic version. External cephalic version involves one or two members of your health care team putting pressure on your belly with their hands to get the baby to roll into a head-down position.

If the procedure isn't successful, or if the baby moves back into a transverse lie, talk with a member of your health care team about the choices you have for delivery. Many babies who are in a transverse lie are born by C-section.

If you're pregnant with twins and only the twin that's lower in the uterus is head down, as shown below, your health care provider may first deliver that baby vaginally.

Then, in some cases, your health care team may suggest delivering the second twin in the breech position. Or they may try to move the second twin into a head-down position. This is done using a procedure called external cephalic version. External cephalic version involves one or two members of the health care team putting pressure on your belly with their hands to get the baby to roll into a head-down position.

Your health care team may suggest delivery by C-section for the second twin if:

An attempt to deliver the baby in the breech position is not successful.
You do not want to try to have the baby delivered vaginally in the breech position.
An attempt to move the baby into a head-down position is not successful.
You do not want to try to move the baby to a head-down position.

In some cases, your health care team may advise that you have both twins delivered by C-section. That might happen if the lower twin is not head down, the second twin has low or high birth weight as compared to the first twin, or if preterm labor starts.

Landon MB, et al., eds. Normal labor and delivery. In: Gabbe's Obstetrics: Normal and Problem Pregnancies. 8th ed. Elsevier; 2021. https://www.clinicalkey.com. Accessed May 19, 2023.
Holcroft Argani C, et al. Occiput posterior position. https://www.updtodate.com/contents/search. Accessed May 19, 2023.
Frequently asked questions: If your baby is breech. American College of Obstetricians and Gynecologists https://www.acog.org/womens-health/faqs/if-your-baby-is-breech. Accessed May 22, 2023.
Hofmeyr GJ. Overview of breech presentation. https://www.updtodate.com/contents/search. Accessed May 22, 2023.
Strauss RA, et al. Transverse fetal lie. https://www.updtodate.com/contents/search. Accessed May 22, 2023.
Chasen ST, et al. Twin pregnancy: Labor and delivery. https://www.updtodate.com/contents/search. Accessed May 22, 2023.
Cohen R, et al. Is vaginal delivery of a breech second twin safe? A comparison between delivery of vertex and non-vertex second twins. The Journal of Maternal-Fetal & Neonatal Medicine. 2021; doi:10.1080/14767058.2021.2005569.
Marnach ML (expert opinion). Mayo Clinic. May 31, 2023.

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Fetal Presentation, Position, and Lie (Including Breech Presentation)

Variations in Fetal Position and Presentation |

During pregnancy, the fetus can be positioned in many different ways inside the mother's uterus. The fetus may be head up or down or facing the mother's back or front. At first, the fetus can move around easily or shift position as the mother moves. Toward the end of the pregnancy the fetus is larger, has less room to move, and stays in one position. How the fetus is positioned has an important effect on delivery and, for certain positions, a cesarean delivery is necessary. There are medical terms that describe precisely how the fetus is positioned, and identifying the fetal position helps doctors to anticipate potential difficulties during labor and delivery.

Presentation refers to the part of the fetus’s body that leads the way out through the birth canal (called the presenting part). Usually, the head leads the way, but sometimes the buttocks (breech presentation), shoulder, or face leads the way.

Position refers to whether the fetus is facing backward (occiput anterior) or forward (occiput posterior). The occiput is a bone at the back of the baby's head. Therefore, facing backward is called occiput anterior (facing the mother’s back and facing down when the mother lies on her back). Facing forward is called occiput posterior (facing toward the mother's pubic bone and facing up when the mother lies on her back).

Lie refers to the angle of the fetus in relation to the mother and the uterus. Up-and-down (with the baby's spine parallel to mother's spine, called longitudinal) is normal, but sometimes the lie is sideways (transverse) or at an angle (oblique).

For these aspects of fetal positioning, the combination that is the most common, safest, and easiest for the mother to deliver is the following:

Head first (called vertex or cephalic presentation)

Facing backward (occiput anterior position)

Spine parallel to mother's spine (longitudinal lie)

Neck bent forward with chin tucked

Arms folded across the chest

If the fetus is in a different position, lie, or presentation, labor may be more difficult, and a normal vaginal delivery may not be possible.

Variations in fetal presentation, position, or lie may occur when

The fetus is too large for the mother's pelvis (fetopelvic disproportion).

The uterus is abnormally shaped or contains growths such as fibroids .

The fetus has a birth defect .

There is more than one fetus (multiple gestation).

Position and Presentation of the Fetus

Toward the end of pregnancy, the fetus moves into position for delivery. Normally, the presentation is vertex (head first), and the position is occiput anterior (facing toward the pregnant person's spine) and with the face and body angled to one side and the neck flexed.

Variations in fetal presentations include face, brow, breech, and shoulder. Occiput posterior position (facing forward, toward the mother's pubic bone) is less common than occiput anterior position (facing backward, toward the mother's spine).

Variations in Fetal Position and Presentation

Some variations in position and presentation that make delivery difficult occur frequently.

Occiput posterior position

In occiput posterior position (sometimes called sunny-side up), the fetus is head first (vertex presentation) but is facing forward (toward the mother's pubic bone—that is, facing up when the mother lies on her back). This is a very common position that is not abnormal, but it makes delivery more difficult than when the fetus is in the occiput anterior position (facing toward the mother's spine—that is facing down when the mother lies on her back).

When a fetus faces up, the neck is often straightened rather than bent,which requires more room for the head to pass through the birth canal. Delivery assisted by a vacuum device or forceps or cesarean delivery may be necessary.

Breech presentation

In breech presentation, the baby's buttocks or sometimes the feet are positioned to deliver first (before the head).

When delivered vaginally, babies that present buttocks first are more at risk of injury or even death than those that present head first.

The reason for the risks to babies in breech presentation is that the baby's hips and buttocks are not as wide as the head. Therefore, when the hips and buttocks pass through the cervix first, the passageway may not be wide enough for the head to pass through. In addition, when the head follows the buttocks, the neck may be bent slightly backwards. The neck being bent backward increases the width required for delivery as compared to when the head is angled forward with the chin tucked, which is the position that is easiest for delivery. Thus, the baby’s body may be delivered and then the head may get caught and not be able to pass through the birth canal. When the baby’s head is caught, this puts pressure on the umbilical cord in the birth canal, so that very little oxygen can reach the baby. Brain damage due to lack of oxygen is more common among breech babies than among those presenting head first.

In a first delivery, these problems may occur more frequently because a woman’s tissues have not been stretched by previous deliveries. Because of risk of injury or even death to the baby, cesarean delivery is preferred when the fetus is in breech presentation, unless the doctor is very experienced with and skilled at delivering breech babies or there is not an adequate facility or equipment to safely perform a cesarean delivery.

Breech presentation is more likely to occur in the following circumstances:

Labor starts too soon (preterm labor).

The uterus is abnormally shaped or contains abnormal growths such as fibroids .

Breech, posterior, transverse lie: What position is my baby in?

Fetal presentation, or how your baby is situated in your womb at birth, is determined by the body part that's positioned to come out first, and it can affect the way you deliver. At the time of delivery, 97 percent of babies are head-down (cephalic presentation). But there are several other possibilities, including feet or bottom first (breech) as well as sideways (transverse lie) and diagonal (oblique lie).

Fetal presentation and position

During the last trimester of your pregnancy, your provider will check your baby's presentation by feeling your belly to locate the head, bottom, and back. If it's unclear, your provider may do an ultrasound or an internal exam to feel what part of the baby is in your pelvis.

Fetal position refers to whether the baby is facing your spine (anterior position) or facing your belly (posterior position). Fetal position can change often: Your baby may be face up at the beginning of labor and face down at delivery.

Here are the many possibilities for fetal presentation and position in the womb.

Medical illustrations by Jonathan Dimes

Head down, facing down (anterior position)

A baby who is head down and facing your spine is in the anterior position. This is the most common fetal presentation and the easiest position for a vaginal delivery.

This position is also known as "occiput anterior" because the back of your baby's skull (occipital bone) is in the front (anterior) of your pelvis.

Head down, facing up (posterior position)

In the posterior position , your baby is head down and facing your belly. You may also hear it called "sunny-side up" because babies who stay in this position are born facing up. But many babies who are facing up during labor rotate to the easier face down (anterior) position before birth.

Posterior position is formally known as "occiput posterior" because the back of your baby's skull (occipital bone) is in the back (posterior) of your pelvis.

Frank breech

In the frank breech presentation, both the baby's legs are extended so that the feet are up near the face. This is the most common type of breech presentation. Breech babies are difficult to deliver vaginally, so most arrive by c-section .

Some providers will attempt to turn your baby manually to the head down position by applying pressure to your belly. This is called an external cephalic version , and it has a 58 percent success rate for turning breech babies. For more information, see our article on breech birth .

Complete breech

A complete breech is when your baby is bottom down with hips and knees bent in a tuck or cross-legged position. If your baby is in a complete breech, you may feel kicking in your lower abdomen.

Incomplete breech

In an incomplete breech, one of the baby's knees is bent so that the foot is tucked next to the bottom with the other leg extended, positioning that foot closer to the face.

Single footling breech

In the single footling breech presentation, one of the baby's feet is pointed toward your cervix.

Double footling breech

In the double footling breech presentation, both of the baby's feet are pointed toward your cervix.

Transverse lie

In a transverse lie, the baby is lying horizontally in your uterus and may be facing up toward your head or down toward your feet. Babies settle this way less than 1 percent of the time, but it happens more commonly if you're carrying multiples or deliver before your due date.

If your baby stays in a transverse lie until the end of your pregnancy, it can be dangerous for delivery. Your provider will likely schedule a c-section or attempt an external cephalic version , which is highly successful for turning babies in this position.

Oblique lie

In rare cases, your baby may lie diagonally in your uterus, with his rump facing the side of your body at an angle.

Like the transverse lie, this position is more common earlier in pregnancy, and it's likely your provider will intervene if your baby is still in the oblique lie at the end of your third trimester.

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Ahmad A et al. 2014. Association of fetal position at onset of labor and mode of delivery: A prospective cohort study. Ultrasound in obstetrics & gynecology 43(2):176-182. https://www.ncbi.nlm.nih.gov/pubmed/23929533 Opens a new window [Accessed September 2021]

Gray CJ and Shanahan MM. 2019. Breech presentation. StatPearls. https://www.ncbi.nlm.nih.gov/books/NBK448063/ Opens a new window [Accessed September 2021]

Hankins GD. 1990. Transverse lie. American Journal of Perinatology 7(1):66-70. https://www.ncbi.nlm.nih.gov/pubmed/2131781 Opens a new window [Accessed September 2021]

Medline Plus. 2020. Your baby in the birth canal. U.S. National Library of Medicine. https://medlineplus.gov/ency/article/002060.htm Opens a new window [Accessed September 2021]

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Sonography fetal assessment, protocols, and interpretation.

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Continuing Education Activity

Fetal ultrasonography is a standard and vital component of a comprehensive fetal evaluation in pregnancy. There are specific indications for using ultrasound in each trimester and assessing both the fetus and the mother by ultrasonography. Based on maternal and fetal risk factors, ultrasound timing and frequency are individualized to evaluate the fetal components at the highest risk for fetal anomalies. Understanding the types of fetal assessments and their indications in each trimester permits earlier detection and diagnosis of fetal anomalies allowing for a multidisciplinary management approach. This activity reviews the classifications and indications of fetal ultrasounds in each trimester and highlights the role of the interprofessional team in identifying the opportunities to screen and diagnose fetal anomalies to maximize patient autonomy and clinical outcomes.

Review the terminology of fetal ultrasonography in pregnancy.
Outline the clinical indications for standard and specialized ultrasounds by trimester.
Describe the scanning protocol and techniques for a detailed first-trimester ultrasound and compare the components of a standard versus detailed second-trimester anatomy scan.
Summarize the clinical implications of common fetal ultrasound abnormalities and their utility by an interprofessional team.
Introduction

Fetal ultrasonography is an essential element in the evaluation of anomalies and fetal well-being throughout pregnancy. The increasing incidence of morbid obesity, hypertension, and gestational diabetes within the reproductive age group places this high-risk population at increased adverse fetal events such as stillbirth and fetal anomalies. In every trimester, there are specific maternal and fetal indications that require additional fetal screening and assessment. [1]

Each fetal scan has been standardized to include the minimal imaging criteria and components required by the society guidelines of American College of Radiology (ACR), Society of Radiologists in Ultrasound (SRU), American College of Obstetrics and Gynecology (ACOG), and American Institute of Ultrasound in Medicine (AIUM), in support by Society of Maternal-Fetal Medicine (SMFM). Although the ultrasound components are standardized, the terminology for the ultrasounds often differs between societies and the Current Procedural Terminology (CPT) descriptions, leading to a long history of misunderstanding amongst clinicians and missed opportunities for fetal assessment. [2]

The above-aforementioned societies agree on the classification of fetal ultrasounds as either standard, specialized, or limited examinations to try and mitigate the ongoing confusion. The standard, specialized, and limited ultrasound criteria can be applied to each trimester. Each examination has specific indications based on the trimester, which must be met before performing the exam. [2] [1]

The standard second-trimester scan, also known as a “level I,” is a simple fetal anatomic survey examination performed in low-risk pregnancies. The specialized second-trimester anatomy ultrasound, also known as “level II,” “detailed,” or “targeted” examination, is performed when abnormalities are suspected on the standard anatomy examination or in pregnancies at high risk for anatomic abnormalities. Other types of specialized examinations include a fetal echocardiogram, fetal doppler ultrasound, cervical length measurement, and biophysical profile. Finally, a limited ultrasound is performed to answer a specific clinical question in any trimester that may aid in the diagnosis and treatment. A limited ultrasound is usually performed in an acute setting when time is restricted or a follow-up to assess specific fetal components. [2] [1]

Fetal ultrasonography is a standard and routine modality performed in every pregnancy. However, the differences in approach, assessment protocols, timing, and frequency of the examinations are individualized based on the gestational age and clinical scenario. The goal of more frequent examinations in the high-risk population is to detect abnormalities in the early stage when further intervention may still be feasible. Traditionally, a comprehensive fetal anatomic survey has been performed in the mid-second trimester to assess anatomic anomalies. Owning to improvement and advancement in ultrasonography, abnormalities can now be detected in the late first trimester. Early identification of fetal anomalies allows the patient to pursue diagnostic testing, genetic counseling, and adequate time to make an informed decision. [3] [4]

Given the broad nature of this topic, the purpose of this article is to review the indications and protocols for a standard versus specialized or “detailed” fetal ultrasound by each trimester. By recognizing the indications and understanding the differences in the fetal components assessed, clinicians will be able to correctly identify the most optimal examination based on gestational age for each patient and improve clinical outcomes.

Anatomy and Physiology

The gestational sac is the first sign of a developing pregnancy, usually identifiable at approximately five weeks gestation. The sac is a round fluid collection that at times is surrounded by two echogenic rings representing the layers of decidua, also known as the double decidual sac sign. When the gestational sac is located on one side of the endometrium and surrounded by an echogenic area, this is known as the intradecidual sign. The absence of these signs does not rule out an intrauterine pregnancy. Visualization of any round or oval fluid collection within the mid-uterus likely represents an intrauterine pregnancy. However, a gestational sac must be distinguished from a “pseudogestational sac” in cases of a suspected ectopic pregnancy. The fluid from the ectopic pregnancy collects in the uterus and mimics a gestational sac. These collections usually contain irregular borders or debris. [5] [6]

The yolk sac is a thin-walled circular structure that develops within the gestational sac, usually after 5.5 weeks of gestation, and usually resolves by 12 weeks. The yolk sac provides nutrition and gas exchange to the developing embryo. The embryo, typically visible at approximately six weeks gestation, is connected to the yolk sac at the midgut via the yolk stalk. The embryo’s first distinguishable structure is the flickering cardiac activity that should develop by a crown-rump length of 7 mm in a normal pregnancy. The presence of a gestational sac with a yolk sac or an embryo is required for a definitive diagnosis of pregnancy. [7] [5]

By 11 weeks gestation, organogenesis is complete, and most fetal anomalies have already formed by this period. Fetal anomalies are present in 2 to 3% of pregnancies, and traditionally a comprehensive fetal anatomic survey has been performed in the mid-second trimester to assess these anomalies. Due to improvement and advancement in ultrasonography, these anomalies can now be seen in the late first trimester. The common malformations of neural tube defects (anencephaly, myelomeningoceles), cystic hygromas, abdominal wall defects, limb abnormalities, and holoprosencephaly can be seen 50% of the time in singleton pregnancies at this early gestational period. Additionally, markers of aneuploidy such as hypoplastic nasal bone, abnormal cardiac findings, abnormal ductus venosus flow can be seen. However, brain structures (cavum septum pellucidum or corpus callosum) or diaphragmatic hernias are not fully developed at this stage and must be evaluated in the mid-second trimester. It is important to note that the early appearance of developing organ structures can be mistaken as anomalies to the untrained eye. For example, before 13 weeks, there is a physiological bowel herniation into the base of the umbilical cord and can be mistaken as an abdominal wall defect if specialized training is not completed before the interpretation of a late first-trimester anatomy scan. [4] [3] [5]

In addition to a comprehensive fetal anatomic evaluation, evaluation of the placenta, including location, texture, and cord insertion, is assessed. If placenta accreta spectrum (PAS) is suspected or a low-lying placenta is visualized on a transabdominal exam, a transvaginal approach for evaluating the placenta is recommended. Suspicion for PAS is based on clinical risks factors such as previous cesarean deliveries in addition to ultrasounds findings. In the first trimester, low implantation of the gestational sac could represent cesarean scar implantation and increase the risk of PAS. In the second and third trimesters, the presence of placenta previa in addition to placental findings of lacunae, disruption in the retroplacental hypoechoic zone, myometrial thinning, or uterovesical hypervascularity greatly increases the likelihood of PAS. The presence of placenta previa with suspicion for PAS markedly increases maternal and fetal mortality, and cesarean delivery is recommended. Detection allows for early multidisciplinary cesarean delivery planning at a tertiary care center where experienced and specialized surgeons are available. [8] [9]

Lastly, maternal pelvic anatomy(uterus, cervix, ovaries, adnexa) is assessed. Evaluation for abnormalities such as fibroids, adnexal masses, Mullerian duct anomalies is evaluated in the first trimester and mid-second trimester scans. The presence of ultrasound abnormalities or clinical indications can lead to additional specialized ultrasound examinations such as serial transvaginal cervical lengths or limited follow-up imaging. [1]

Indications

Standard First-Trimester Ultrasound Examination

As outlined by the AIUM-ACR-ACOG-SMFM-SRU practice parameters, indications include confirmation of singleton/multiple gestation intrauterine pregnancy and chorionicity/amnionicity if applicable, confirmation of cardiac activity, estimation of gestational age, evaluation of suspected ectopic pregnancy, measurement of Nuchal Translucency (NT) for aneuploidy screening, vaginal bleeding, pelvic pain, suspected gestational trophoblastic disease, or maternal pelvic organ assessment. [1]

Detailed First-Trimester Anatomy Ultrasound Examination (Early Comprehensive Fetal Anatomy Ultrasound)

This specialized diagnostic examination is an indication-driven examination for women at increased risk of fetal and/or placental anomalies performed between 12 weeks and 0 days to 13 weeks and six days either transabdominally or combined with the transvaginal approach. Indications include a previous child with an anomaly, increased Nuchal Translucency >3 mm, a suspected fetal anomaly in the current pregnancy, advanced maternal age, pregestational diabetes mellitus, maternal obesity, IVF pregnancy, teratogen exposure, congenital infection exposures, multifetal gestation, positive maternal serum screening tests, abnormal placental implantation. The best time to perform an early anatomy scan is after 13 weeks. With great emphasis, this ultrasound does not replace a detailed second-trimester anatomic survey, which should always be performed. [4] [10]

Standard Second-Trimester Anatomy Ultrasound Examination

This routine anatomy ultrasound is performed between 18 to 22 weeks in every pregnancy to assess fetal anatomy, screen for anomalies, evaluate the placental location and maternal pelvic anatomy, and estimate gestational age (if not performed with an earlier scan). The standard anatomical ultrasound is performed in low-risk pregnancies who otherwise do not have indications for a detailed anatomy scan, as outlined below. [1]

Detailed Second Trimester Anatomy Ultrasound Examination

According to the AIUM-ACR-ACOG-SMFM-SRU practice parameters, this scan is an indication-driven examination and is not intended to be performed in all pregnancies. The indications include a previous child with an anomaly, increased Nuchal Translucency >3 mm, a suspected fetal anomaly in current pregnancy, advanced maternal age, pregestational diabetes mellitus, early gestational diabetes before 24 weeks, maternal obesity, IVF pregnancy, teratogen exposure, congenital infection exposures, multifetal gestation, positive maternal serum screening tests, abnormal placental implantation, parental chromosomal/genetic carrier, aneuploidy marker on previous ultrasound, alloimmunization, oligohydramnios, polyhydramnios, maternal drug use. [11]

Specialized Third Trimester Ultrasound Examination

Third-trimester ultrasounds are indication-driven examinations. Examples of types of specialized ultrasounds include the biophysical profile, additional biometric measurements follow-ups (every 3 to 4 weeks), doppler ultrasounds in the setting of growth restrictions. Indications include fetal growth restriction or suspected macrosomia, multifetal gestation, twin-twin transfusion syndrome screening (every two weeks), a significant discrepancy between the uterine size and clinical dates, evaluation of fetal well-being, evaluation of prelabour rupture of membranes, preterm labor, vaginal bleeding, suspected placental abruption, follow-up evaluation for placental appearance for suspected placenta previa, vasa previa, PAS, suspected fetal death, suspected amniotic fluid abnormalities. [1] [12]

Contraindications

The absolute contraindication to performing fetal ultrasonography is patient refusal. Ultrasonography is generally safe during pregnancy and should only be used when indicated with the physician’s order under the ALARA (as low as reasonably achievable) principle. M-mode imaging should be used for documentation of cardiac activity, and pulse doppler is discouraged if it will not add valuable information to the examination. [4]

Most examinations are performed with gray-scale real-time scanners using a transabdominal or transvaginal approach. The approach is influenced by gestational age, maternal habitus, and fetal positioning. Abdominal curvilinear transducer with 3 to 5 MHz provides enough penetration to achieve adequate resolution. Additionally, high-frequency probes (9 to 12 MHz) are used for the transvaginal approach. [4] [13]

According to the AIUM's accreditation policies, sonographers are required to be credentialed in their practicing specialty. Ultrasound examinations are supervised by a licensed medical provider who meets the training specialty guidelines, and a qualified physician should be readily available to interpret the ultrasound examination. [3]

Additionally, according to "Training Guidelines for Physicians Who Evaluate and Interpret Diagnostic Obstetric Ultrasound Examinations," physicians and sonographers who read and perform Early Comprehensive Fetal Anatomy Ultrasounds should undergo specialized training at a teaching facility that will allow the adequate experience to become proficient. Performance of early comprehensive fetal anatomy ultrasounds should be done within referral centers with specialized expertise in reading and counseling patients on findings. [3]

Preparation

Before starting any ultrasound examination, the sonographer should confirm the correct patient, the scan to be performed, and the reason for the scan. For transabdominal ultrasounds, the patient should ideally have a full bladder for resolution enhancement of surrounding structures. For a transvaginal approach, the bladder should be empty for optimal visualization. [13]

Technique or Treatment

The Detailed First-Trimester Anatomy Ultrasound Examination is a relatively new recommendation by the AIUM-ACR-ACOG-SMFM-SRU practice parameter that has yet to be adopted as the standard of care in those who meet indications. Techniques and imaging parameters will be discussed in this section. A combined transabdominal and transvaginal approach may be needed to visualize all structures fully.

Fetal Biometry

The techniques for assessing fetal biometry via crown-rump length or biparietal diameter (BPD) and head circumference (HC) are standard and are unchanged from AIUM-ACR-ACOG-SMFM practice parameters. [10] [14]

Sagittal and axial planes are used for the evaluation of the fetal head structures. The skull should be oval with calvarial ossification and no bulges. The choroid plexus should be visible on each side of the falx cerebri in the transventricular plane. In the transthalamic plane, the thalami, cerebral peduncles, third ventricle, and aqueduct of Sylvius are visualized. Angling toward the posterior fossa in the axial plane allows for visualization of the fourth ventricle. The thalami, midbrain, brain stem, fourth ventricle, and future cisterna magna should also be visualized in this plane. [10] [15]

Potential abnormalities: Within the midsagittal view, signs of early spina bifida are seen if the future cisterna magna appears abnormal or the fourth ventricle is absent or compressed. Posterior displacement of the aqueduct of Sylvius is also a marker for spina bifida. Enlargement of the fourth ventricle can be associated with the Dandy-Walker continuum. Anencephaly-acrania sequence, alobar holoprosencephaly, and large cephaloceles can also be detected during this period. [10] [16] [17] [18] [15]

Limitations: The cavum septum pellucidum and corpus callosum are not visible in the late first trimester. [10]

Face and Profile

The forehead, nasal bridge, nasal bone, maxilla, and mandible should be seen in the midsagittal and views. The forehead should not be protruding or flattened, and there should be a contiguous nose to upper lip contour without maxillary protuberance or gap. The nasal bones, premaxillary processes, primary palate, and mandible can be identified by the retronasal triangle. The coronal plane is used to visualize the orbits, lenses, and upper lip integrity. [10]

Potential abnormalities: A maxillary gap is suspicious for a cleft palate. The absence of the mandibular gap is suspicious for micrognathia. [19] [20]

In an axial or coronal view, the neck should be evaluated for abnormal fluid collections, cystic hygroma, or dilated jugular lymphatic sacs. The midsagittal plane is used to evaluate the nuchal translucency. Precise measurement is only required if the nuchal translucency (NT) appears enlarged or is a part of a screening for aneuploidy. There are established guidelines for the measurement of nuchal translucency to reduce false-negative and false-positive values. Guidelines for NT measurement are outlined by the AIUM-ACR-ACOG-SMFM-SRU Practice Parameter. [1]

Thorax and Heart

The required structures in the axial view are cardiac position and axis, 4-chamber view without and with color Doppler, 3-vessel and trachea view with color Doppler, symmetric lungs, and diaphragm demarcation. In the coronal and sagittal view, diaphragm demarcation should also be visualized. Though color Doppler should be limited during the first trimester, color flow is essential for the visualization of the heart structures at this gestation age. Output display standard should be monitored to keep the thermal index for bone <0.7. [10] [13]

In the axial view, the lungs should be symmetric, and the ribs should appear of normal ossification and length. The heart should be one-third the size of the chest. The four-chamber view with color Doppler should show equal-sized ventricles, with defined ventricular septum, atria, and demonstration of mitral and tricuspid flow. The three-vessel and trachea view with color Doppler should show transverse aortic arch/isthmus merging with the pulmonary trunk/ductus arteriosus. There should be antegrade flow to the left side of the trachea. In patients with suspected cardiac abnormalities, longitudinal aortic and ductal arches with pulsed wave Doppler flow may be performed. [10] [21] [22]

Abdomen and Pelvis

The axial plane at the levels of the stomach, kidneys, and bladder are evaluated. The orientation of the abdomen should contain the stomach on the left and the liver on the right side, with the portal vein going away from the stomach. The umbilical cord insertion into the anterior abdominal wall is evaluated. It is important to note that physiologic herniation of the bowel into the umbilical cord base is seen before 13 weeks and is not associated with anomalies. The bladder should contain fluid. If the kidneys are not visualized in the coronal view, renal artery power or color Doppler imaging is recommended. [23] [10]

Potential Abnormalities: Cystic collections within the abdomen or enlarged bladder >7 mm could indicate aneuploidy or urinary tract obstruction. [10] [24]

Spine and Extremities

Three long bones should be identified in each extremity. Feet and hands should be documented. Detailed assessment of fingers/toes is required if an abnormality is suspected. The spine is evaluated in the longitudinal and axial planes with attention to scoliosis or irregularity. If skeletal dysplasia is suspected, calvarial shape, thorax, ribs, the scapula should be evaluated. [25] [10]

Limitation: The distal spine is not completely ossified at this gestational period. [10]

Placenta, Uterus, and Adnexa

The placental position relative to the lower uterine segment, umbilical cord insertion, and echotexture must be evaluated. If there is suspicion for PAS, a transvaginal approach with a partially full bladder should be performed with color Doppler and myometrial thinning, bladder wall interface; uterine vesicular vascularity abnormalities should be documented. Leiomyomata size, location, and number should be documented. Ovaries, adnexa, and the cul-de-sac should be visualized. Any Mullerian duct anomalies should be documented. [10] [26] [27]

The components of a Standard Second-Trimester Anatomy Examination and Detailed Second Trimester Anatomy Examination are summarized in the tables at the end of this article. A detailed, comprehensive anatomy scan includes all of the components of the standard anatomy scan with additional specific components guided by the initial indication for the scan. Also, specific ultrasound findings during the standard anatomy scan can direct additional detailed anatomic evaluation as determined by the reading physician. Therefore, not all of the components listed in the detailed description may be indicated in every detailed anatomic scan. Clinical judgment is warranted. [11]

Complications

There are no major risks or complications to the fetus or mother undergoing a transabdominal ultrasound. A potential complication in the transvaginal approach is the possibility of inadvertently inserting the probe through the cervical os, causing a hemorrhage in the setting of an unknown placenta previa or vasa previa. However, this risk is very low if the scan provider or sonographer is properly credentialed and trained in the technique. Taking precautions by starting each examination with the transabdominal approach to locate the placenta can avoid this possible risk.

Clinical Significance

Screening for fetal anomalies is performed in the first and second trimester by a nuchal translucency screening, maternal serum cell-free DNA, or serum quad screen testing. When the screening test results are abnormal or suspicious for aneuploidy, diagnostic karyotyping is offered, in addition to a detailed anatomic ultrasound, evaluation to look for structural anomalies, which can be performed in the late first trimester. Findings of cystic hygroma, short femur, coarctation of the aorta, hypoplastic left heart, renal anomalies, cardiac defects, abdominal wall hernias are highly suspicious for aneuploidy, especially when combined and should prompt further diagnostic testing. [4] [3]

Diagnostic testing is outside of the scope of this topic but includes chorionic villus sampling performed between 10 to 13 weeks gestation and amniocentesis, which is optimally performed between 15 to 20 weeks of gestation. Depending on the state law, if a genetic abnormality incompatible with life is diagnosed before the third trimester, patients may have more reproductive options. Diagnosing major fetal abnormalities that will require immediate postnatal surgical intervention decreases morbidity and mortality when a multidisciplinary approach is taken to facilitate proper care and resources. [4]

Abnormalities in screening tests are not always associated with aneuploidy but can be markers of adverse pregnancy outcomes. For example, enlarged NT is associated with miscarriage, intrauterine death, or congenital heart defects. The risk of adverse outcomes is proportional to the degree of NT enlargement. An increased thickness above 3.0 mm (or above 99th percentile for crown-rump length) is directly proportional to an increased risk for aneuploidy (Down syndrome and Turner syndrome) and structural abnormalities unrelated related to aneuploidy. Congenital heart disease is the most commonly associated malformation in fetuses with euploid karyotypes. Genetic counseling, invasive genetic testing, detailed fetal anatomy scan, and fetal echocardiogram are recommended, and they should be cautiously monitored throughout the antenatal period. [28] [29]

Enhancing Healthcare Team Outcomes

To optimize clinical outcomes, fetal ultrasonography is an essential component in the early detection of fetal anomalies. Beginning with the initial prenatal visit, properly identifying risk factors or exposures by the obstetrician, midwife, or nurse practitioner is important for early ultrasonography evaluation. Communication between the ultrasonographer, obstetrician, and Maternal-Fetal Medicine specialist is vital in diagnosing any major fetal anomalies or maternal complications requiring early intervention or transfer to a tertiary care center equipped with resources to safely handle the management and care of both mother and fetus. [Level 5]

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Components of CPT Code 76811 (Standard and Detailed Examinations) (2019), AIUM Practice Parameter for the Performance of Detailed Second- and Third-Trimester Diagnostic Obstetric Ultrasound Examinations. J Ultrasound Med, 38: 3093-3100. https://doi.org/10.1002/jum.15163. (more...)

Four chamber heart view of a second trimester fetus Contributed by Dawood Tafti, MD

Evaluation of the bladder in a second trimester fetus Contributed by Dawood Tafti, MD

Evaluation of the cerebellum and cisterna magna in a second trimester fetus Contributed by Dawood Tafti, MD

Disclosure: Sanela Andelija declares no relevant financial relationships with ineligible companies.

Disclosure: Dawood Tafti declares no relevant financial relationships with ineligible companies.

This book is distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0) ( http://creativecommons.org/licenses/by-nc-nd/4.0/ ), which permits others to distribute the work, provided that the article is not altered or used commercially. You are not required to obtain permission to distribute this article, provided that you credit the author and journal.

Cite this Page Andelija S, Tafti D. Sonography Fetal Assessment, Protocols, and Interpretation. [Updated 2023 May 22]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-.

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Fetal Ultrasound

• An imaging study in which high-frequency sound waves create pictures of a fetus inside the uterus
• For viewing the fetus during pregnancy
• It is also utilized to guide procedures such as amniocentesis or chorionic villus sampling
• Involves Ob/Gyn and Maternal-Fetal Medicine
Prenatal Ultrasound Scan

What is ultrasound?

Who performs an ultrasound, how do ultrasounds assist pregnancy, in what other ways is ultrasound used, how do you prepare for an ultrasound, how is yale medicine's use of ultrasound technology unique.

Since the mid-20th century, ultrasound has been used extensively to create a "picture" of what's happening inside our bodies. For pregnant women, it is an indispensable aspect to care.

At Yale Medicine Maternal-Fetal Medicine , our physicians and sonographers perform more than 16,000 ultrasounds a year.

"Experience counts. This is the only way we can approach the fetus like a patient. With sophisticated ultrasound, we now have ways to identify fetal problems and guide treatment," says Joshua Copel, MD , a Yale Medicine expert in prenatal diagnosis and fetal therapy. "If a baby has an abnormal amount of fluid in the chest, we can use an ultrasound-guided needle to drain it out. Or we can deliver blood to the umbilical cord. The first of these types of transfusions were done here at Yale in 1984."

Think of ultrasound—sometimes called a sonogram—as sonar for the body. A small instrument called a “transducer” transmits high-frequency sound waves, bouncing them off structures in the body and using the reflected sound waves to paint a picture.

The sound waves can determine the distance, size, shape and consistency of an object. A computer compiles these results to create an image of the object, be it a fetus, an adult heart, or a tumor in the kidney.

Specially trained physicians and sonographers perform ultrasounds by spreading gel on the skin adjacent to the body part to be imaged. (The gel helps to conduct the sound waves and makes it easier to move the transducer over the skin.) Most ultrasound procedures are painless and non-invasive.

Ultrasound imaging has been used for decades and has an excellent safety record. It’s important to remember that ultrasound uses sound waves; it does not use ionizing radiation, like X-rays, which can cause harm after prolonged exposure

Ultrasound is the most widely used medical imaging method for viewing a fetus during pregnancy. It is also utilized to guide procedures such as amniocentesis or chorionic villus sampling .

An ultrasound may be done at almost any time during a pregnancy, even as early as about five weeks after conception. During the first trimester, it can confirm a viable pregnancy and heartbeat, measure the distance from the head to the rear end in order to confirm gestational age, and identify problems such as molar or ectopic pregnancies. It can also identify some uterine or pelvic problems in the mother.

In the second trimester, ultrasound can pinpoint fetal malformations, confirm multiple pregnancies (though this is ideally done in the first trimester), monitor levels of amniotic fluid and evaluate how well the fetus is doing.

In the third trimester, ultrasound can show the placenta's placement, how the fetus is moving and presented for birth, and measure how well the baby is growing.

Abdominal ultrasound can create images of abdominal tissues and organs.
Ultrasound may guide surgeons as they perform biopsies and other procedures.
Ultrasound may map brain structures.
Ultrasound can visualize the interior of the ear or the eye.
Ultrasound can find clots in veins in the leg.
It can find bleeding in the abdomen or chest after a motor vehicle accident.

There is no special preparation for a routine ultrasound, though it may make sense to wear loose clothes for comfort. Ultrasounds are painless. Saline used in sonohysterography (a procedure in which saline is injected through the cervix into the uterus, in order to produce a more detailed ultrasound image) occasionally causes mild cramping, but over-the-counter medication is usually enough to manage this pain.

At Yale Medicine, we are skilled at using ultrasound to guide care.

"Three percent of babies are born with major birth defects, many of which can be identified with ultrasound," says Dr. Copel. "But it's critical to have experienced eyes and hands do the scans. At Yale, we have both the experience and premium-level equipment with better technology than typically found in other settings."

We have pioneered the use of transvaginal ultrasound early in pregnancy, as well as the use of ultrasound to diagnose pelvic pain, breast cancer and ectopic pregnancy. Yale physicians continue to explore the use of ultrasound to map the brain and track the vascular behavior of cancerous tumors.

We are also exploring the use of Doppler ultrasound to monitor cardiovascular conditions.

Labour and Delivery Care Module: 8. Abnormal Presentations and Multiple Pregnancies

Study session 8 abnormal presentations and multiple pregnancies, introduction.

In previous study sessions of this module, you have been introduced to the definitions, signs, symptoms and stages of normal labour, and about the ‘normal’ vertex presentation of the fetus during delivery. In this study session, you will learn about the most common abnormal presentations (breech, shoulder, face or brow), their diagnostic criteria and the required actions you need to take to prevent complications developing during labour. Taking prompt action may save the life of the mother and her baby if the delivery becomes obstructed because the baby is in an abnormal presentation. We will also tell you about twin births and the complications that may result if the two babies become ‘locked’ together, preventing either of them from being born.

Learning Outcomes for Study Session 8

After studying this session, you should be able to:

8.1 Define and use correctly all of the key words printed in bold . (SAQs 8.1 and 8.2)

8.2 Describe how you would identify a fetus in the vertex presentation and distinguish this from common malpresentations and malpositions. (SAQs 8.1 and 8.2)

8.3 Describe the causes and complications for the fetus and the mother of fetal malpresentation during full term labour. (SAQ 8.3)

8.4 Describe how you would identify a multiple pregnancy and the complications that may arise. (SAQ 8.4)

8.5 Explain when and how you would refer a woman in labour due to abnormal fetal presentation or multiple pregnancy. (SAQ 8.4)

8.1 Normal and abnormal presentations

8.1.1 vertex presentation.

In about 95% of deliveries, the part of the fetus which arrives first at the mother’s pelvic brim is the highest part of the fetal head, which is called the vertex (Figure 8.1). This presentation is called the vertex presentation . Notice that the baby’s chin is tucked down towards its chest, so that the vertex is the leading part entering the mother’s pelvis. The baby’s head is said to be ‘well-flexed’ in this position.

A baby in the well-flexed vertex presentation before birth, relative to the mother’s pelvis

During early pregnancy, the baby is the other way up — with its bottom pointing down towards the mother’s cervix — which is called the breech presentation . This is because during its early development, the head of the fetus is bigger than its buttocks; so in the majority of cases, the head occupies the widest cavity, i.e. the fundus (rounded top) of the uterus. As the fetus grows larger, the buttocks become bigger than the head and the baby spontaneously reverses its position, so its buttocks occupy the fundus. In short, in early pregnancy, the majority of fetuses are in the breech presentation and later in pregnancy most of them make a spontaneous transition to the vertex presentation.

8.1.2 Malpresentations

You will learn about obstructed labour in Study Session 9.

When the baby presents itself in the mother’s pelvis in any position other than the vertex presentation, this is termed an abnormal presentation, or m alpresentation . The reason for referring to this as ‘abnormal’ is because it is associated with a much higher risk of obstruction and other birth complications than the vertex presentation. The most common types of malpresentation are termed breech, shoulder, face or brow. We will discuss each of these in turn later. Notice that the baby can be ‘head-down’ but in an abnormal presentation, as in face or brow presentations, when the baby’s face or forehead (brow) is the presenting part.

8.1.3 Malposition

Although it may not be so easy for you to identify this, the baby can also be in an abnormal position even when it is in the vertex presentation. In a normal delivery, when the baby’s head has engaged in the mother’s pelvis, the back of the baby’s skull (the occiput ) points towards the front of the mother’s pelvis (the pubic symphysis ), where the two pubic bones are fused together. This orientation of the fetal skull is called the occipito-anterior position (Figure 8.2a). If the occiput (back) of the fetal skull is towards the mother’s back, this occipito-posterior position (Figure 8.2b) is a vertex malposition , because it is more difficult for the baby to be born in this orientation. The good thing is that more than 90% of babies in vertex malpositions undergo rotation to the occipito-anterior position and are delivered normally.

You learned the directional positions: anterior/in front of and posterior/behind or in the back of, in the Antenatal Care Module, Part 1, Study Session 3.

Note that the fetal skull can also be tilted to the left or to the right in either the occipito-anterior or occipito-posterior positions.

Possible positions of the fetal skull when the baby is in the vertex presentation and the mother is lying on her back:

8.2 Causes and consequences of malpresentations and malpositions

In the majority of individual cases it may not be possible to identify what caused the baby to be in an abnormal presentation or position during delivery. However, the general conditions that are thought to increase the risk of malpresentation or malposition are listed below:

Multiple pregnancy is the subject of Section 8.7 of this study session. You learned about placenta previa in the Antenatal Care Module, Study Session 21.

Abnormally increased or decreased amount of amniotic fluid
A tumour (abnormal tissue growth) in the uterus preventing the spontaneous inversion of the fetus from breech to vertex presentation during late pregnancy
Abnormal shape of the pelvis
Laxity (slackness) of muscular layer in the walls of the uterus
Multiple pregnancy (more than one baby in the uterus)
Placenta previa (placenta partly or completely covering the cervical opening).

If the baby presents at the dilating cervix in an abnormal presentation or malposition, it will more difficult (and may be impossible) for it to complete the seven cardinal movements that you learned about in Study Sessions 3 and 5. As a result, birth is more difficult and there is an increased risk of complications, including:

You learned about PROM in Study Session 17 of the Antenatal Care Module, Part 2.

Premature rupture of the fetal membranes (PROM)
Premature labour
Slow, erratic, short-lived contractions
Uncoordinated and extremely painful contractions, with slow or no progress of labour
Prolonged and obstructed labour, leading to a ruptured uterus (see Study Sessions 9 and 10 of this Module)
Postpartum haemorrhage (see Study Session 11)
Fetal and maternal distress, which may lead to the death of the baby and/or the mother.

With these complications in mind, we now turn your attention to the commonest types of malpresentation and how to recognise them.

8.3 Breech presentation

In a b reech presentation , the fetus lies with its buttocks in the lower part of the uterus, and its buttocks and/or the feet are the presenting parts during delivery. Breech presentation occurs on average in 3–4% of deliveries after 34 weeks of pregnancy.

When is the breech position the normal position for the fetus?

During early pregnancy the baby’s bottom points down towards the mother’s cervix, and its head (the largest part of the fetus at this stage of development) occupies the fundus (rounded top) of the uterus, which is the widest part of the uterine cavity.

8.3.1 Causes of breech presentation

You can see a transverse lie in Figure 8.7 later in this study session.

In the majority of cases there is no obvious reason why the fetus should present by the breech at full term. In practice, what is commonly observed is the association of breech presentation at delivery with a transverse lie earlier in the pregnancy, i.e. the fetus lies sideways across the mother’s abdomen, facing a sideways implanted placenta. It is thought that when the placenta is in front of the baby’s face, it may obstruct the normal process of inversion, when the baby turns head-down as it gets bigger during the pregnancy. As a result, the fetus turns in the other direction and ends in the breech presentation. Some other circumstances that are thought to favour a breech presentation during labour include:

Premature labour, beginning before the baby undergoes spontanous inversion from breech to vertex presentation
Multiple pregnancy, preventing the normal inversion of one or both babies
Polyhydramnios: excessive amount of amniotic fluid, which makes it more difficult for the fetal head to ‘engage’ with the mother’s cervix (polyhydramnios is pronounced ‘poll-ee-hy-dram-nee-oss’. Hydrocephaly is pronounced ‘hy-droh-keff-all-ee’)
Hydrocephaly (‘water on the brain’) i.e. an abnormally large fetal head due to excessive accumulation of fluid around the brain
Placenta praevia
Breech delivery in the previous pregnancy
Abnormal formation of the uterus.

8.3.2 Diagnosis of breech presentation

On abdominal palpation the fetal head is found above the mother’s umbilicus as a hard, smooth, rounded mass, which gently ‘ballots’ (can be rocked) between your hands.

Why do you think a mass that ‘ballots’ high up in the abdomen is a sign of breech presentation? (You learned about this in Study Session 11 of the Antenatal Care Module.)

The baby’s head can ‘rock’ a little bit because of the flexibility of the baby’s neck, so if there is a rounded, ballotable mass above the mother’s umbilicus it is very likely to be the baby’s head. If the baby was ‘bottom-up’ (vertex presentation) the whole of its back will move of you try to rock the fetal parts at the fundus (Figure 8.3).

(a) The whole back of a baby in the vertex position will move if you rock it at the fundus; (b) The head can be ‘rocked’ and the back stays still in a breech presentation.

Once the fetus has engaged and labour has begun, the breech baby’s buttocks can be felt as soft and irregular on vaginal examination. They feel very different to the relatively hard rounded mass of the fetal skull in a vertex presentation. When the fetal membranes rupture, the buttocks and/or feet can be felt more clearly. The baby’s anus may be felt and fresh thick, dark meconium may be seen on your examining finger. If the baby’s legs are extended, you may be able to feel the external genitalia and even tell the sex of the baby before it is born.

8.3.3 Types of breech presentation

There are three types of breech presentation, as illustrated in Figure 8.4. They are:

Complete breech is characterised by flexion of the legs at both hips and knee joints, so the legs are bent underneath the baby.
Frank breech is the commonest type of breech presentation, and is characterised by flexion at the hip joints and extension at the knee joints, so both the baby’s legs point straight upwards.
Footling breech is when one or both legs are extended at the hip and knee joint and the baby presents ‘foot first’.

Figure 8.4 Different types of breech presentation.

8.3.4 Risks of breech presentation

Regardless of the type of breech presentation, there are significant associated risks to the baby. They include:

The fetal head gets stuck (arrested) before delivery
Labour becomes obstructed when the fetus is disproportionately large for the size of the maternal pelvis
Cord prolapse may occur, i.e. the umbilical cord is pushed out ahead of the baby and may get compressed against the wall of the cervix or vagina
Premature separation of the placenta (placental abruption)
Birth injury to the baby, e.g. fracture of the arms or legs, nerve damage, trauma to the internal organs, spinal cord damage, etc.

A breech birth may also result in trauma to the mother’s birth canal or external genitalia through being overstretched by the poorly fitting fetal parts.

Cord prolapse in a normal (vertex) presentation was illustrated in Study Session 17 of the Antenatal Care Module, and placental abruption was covered in Study Session 21.

What will be the effect on the baby if it gets stuck, the labour is obstructed, the cord prolapses, or placental abruption occurs?

The result will be hypoxia , i.e. it will be deprived of oxygen, and may suffer permanent brain damage or die.

You learned about the causes and consequences of hypoxia in the Antenatal Care Module.

8.4 Face presentation

Face presentation occurs when the baby’s neck is so completely extended (bent backwards) that the occiput at the back of the fetal skull touches the baby’s own spine (see Figure 8.5). In this position, the baby’s face will present to you during delivery.

5 Face presentation. (a) The baby’s chin is facing towards the front of the mother’s pelvis; (b) the chin is facing towards the mother’s backbone.

Refer the mother if a baby in the chin posterior face presentation does not rotate and the labour is prolonged.

The incidence of face presentation is about 1 in 500 pregnancies in full term labours. In Figure 8.5, you can see how flexed the head is at the neck. Babies who present in the ‘chin posterior’ position (on the right in Figure 8.5) usually rotate spontaneously during labour, and assume the ‘chin anterior’ position, which makes it easier for them to be born. However, they are unlikely to be delivered vaginally if they fail to undergo spontaneous rotation to the chin anterior position, because the baby’s chin usually gets stuck against the mother’s sacrum (the bony prominence at the back of her pelvis). A baby in this position will have to be delivered by caesarean surgery.

8.4.1 Causes of face presentation

The causes of face presentation are similar to those already described for breech births:

Laxity (slackness) of the uterus after many previous full-term pregnancies
Multiple pregnancy
Polyhydramnios (excessive amniotic fluid)
Congenital abnormality of the fetus (e.g. anencephaly, which means no or incomplete skull bones)
Abnormal shape of the mother’s pelvis.

8.4.2 Diagnosis of face presentation

Face presentation may not be easily detected by abdominal palpation, especially if the chin is in the posterior position. On abdominal examination, you may feel irregular shapes, formed because the fetal spine is curved in an ‘S’ shape. However, on vaginal examination, you can detect face presentation because:

The presenting part will be high, soft and irregular.
When the cervix is sufficiently dilated, you may be able to feel parts of the face, such as the orbital ridges above the eyes, the nose or mouth, gums, or bony chin.
If the membranes are ruptured, the baby may suck your examining finger!

But as labour progresses, the baby’s face becomes o edematous (swollen with fluid), making it more difficult to distinguish from the soft shape you will feel in a breech presentation.

8.4.3 Complications of face presentation

Complications for the fetus include:

Obstructed labour and ruptured uterus
Cord prolapse
Facial bruising
Cerebral haemorrhage (bleeding inside the fetal skull).

8.5 Brow presentation

In brow presentation , the baby’s head is only partially extended at the neck (compare this with face presentation), so its brow (forehead) is the presenting part (Figure 8.6). This presentation is rare, with an incidence of 1 in 1000 deliveries at full term.

8.5.1 Possible causes of brow presentation

You have seen all of these factors before, as causes of other malpresentations:

Lax uterus due to repeated full term pregnancy
Polyhydramnios

8.5.2 Diagnosis of brow presentation

Brow presentation is not usually detected before the onset of labour, except by very experienced birth attendants. On abdominal examination, the head is high in the mother’s abdomen, appears unduly large and does not descend into the pelvis, despite good uterine contractions. On vaginal examination, the presenting part is high and may be difficult to reach. You may be able to feel the root of the nose, eyes, but not the mouth, tip of the nose or chin. You may also feel the anterior fontanel, but a large caput (swelling) towards the front of the fetal skull may mask this landmark if the woman has been in labour for some hours.

Recall the appearance of a normal caput over the posterior fontanel shown in Figure 4.4 earlier in this Module.

8.5.3 Complications of brow presentation

The complications of brow presentation are much the same as for other malpresentations:

Cerebral haemorrhage.

Which are you more likely to encounter — face or brow presentations?

Face presentation, which occurs in 1 in 500 full term labours. Brow presentation is more rare, at 1 in 1,000 full term labours.

8.6 Shoulder presentation

Shoulder presentation is rare at full term, but may occur when the fetus lies transversely across the uterus (Figure 8.7), if it stopped part-way through spontaneous inversion from breech to vertex, or it may lie transversely from early pregnancy. If the baby lies facing upwards, its back may be the presenting part; if facing downwards its hand may emerge through the cervix. A baby in the transverse position cannot be born through the vagina and the labour will be obstructed. Refer babies in shoulder presentation urgently.

8.6.1 Causes of shoulder presentation

Causes of shoulder presentation could be maternal or fetal factors.

Maternal factors include:

Lax abdominal and uterine muscles: most often after several previous pregnancies
Uterine abnormality
Contracted (abnormally narrow) pelvis.

Fetal factors include:

Preterm labour
Placenta previa.

What do ‘placenta previa’ and ‘polyhydramnios’ indicate?

Placenta previa is when the placenta is partly or completely covering the cervical opening. Polyhydramnios is an excess of amniotic fluid. They are both potential causes of malpresentation.

8.6.2 Diagnosis of shoulder presentation

On abdominal palpation, the uterus appears broader and the height of the fundus is less than expected for the period of gestation, because the fundus is not occupied by either the baby’s head or buttocks. You can usually feel the head on one side of the mother’s abdomen. On vaginal examination, in early labour, the presenting part may not be felt, but when the labour is well progressed, you may feel the baby’s ribs. When the shoulder enters the pelvic brim, the baby’s arm may prolapse and become visible outside the vagina.

8.6.3 Complications of shoulder presentation

Complications include:

Trauma to a prolapsed arm
Fetal hypoxia and death.

Remember that a shoulder presentation means the baby cannot be born through the vagina; if you detect it in a woman who is already in labour, refer her urgently to a higher health facility.

8.7 Multiple pregnancy

In this section, we turn to the subject of multiple pregnancy , when there is more than one fetus in the uterus. More than 95% of multiple pregnancies are twins (two fetuses), but there can also be triplets (three fetuses), quadruplets (four fetuses), quintuplets (five fetuses), and other higher order multiples with a declining chance of occurrence. The spontaneous occurrence of twins varies by country : it is lowest in East Asia n countries like Japan and China (1 out of 1000 pregnancies are fraternal or non-identical twins), and highest in black Africans , particularly in Nigeria , where 1 in 20 pr egnancies are fraternal twins. In general, compared to single babies, multiple pregnancies are highly associated with early pregnancy loss and high perinatal mortality, mainly due to prematurity.

8.7.1 Types of twin pregnancy

Twins may be identical (monozygotic) or non-identical and fraternal (dizigotic). Monozygotic twins develop from a single fertilised ovum (the zygote), so they are always the same sex and they share the same placenta . By contrast, dizygotic twins develop from two different zygotes, so they can have the same or different sex, and they have separate placenta s . Figure 8.8 shows the types of twin pregnancy and the processes by which they are formed.

Types of twin pregnancy: (a) Fraternal or non-identical twins usually each have a placenta of their own, although they can fuse if the two placentas lie very close together. (b) Identical twins always share the same placenta, but usually they have their own fetal membranes.

8.7.2 Diagnosis of twin pregnancy

On abdominal examination you may notice that:

The size of the uterus is larger than the expected for the period for gestation.
The uterus looks round and broad, and fetal movement may be seen over a large area. (The shape of the uterus at term in a singleton pregnancy in the vertex presentation appears heart-shaped rounder at the top and narrower at the bottom.)
Two heads can be felt.
Two fetal heart beats may be heard if two people listen at the same time, and they can detect at least 10 beats different (Figure 8.6).
Ultrasound examination can make an absolute diagnosis of twin pregnancy.

Two people listen either side of the pregnant woman. Each taps in rhythm with the heartbeat they can hear. The pregnant woman says that their tapping is different and maybe she is having twins.

8.7.3 Consequences of twin pregnancy

Women who are pregnant with twins are more prone to suffer with the minor disorders of pregnancy, like morning sickness, nausea and heartburn. Twin pregnancy is one cause of hyperemesis gravidarum (persistent, severe nausea and vomiting). Mothers of twins are also more at risk of developing iron and folate-deficiency anaemia during pregnancy.

Can you suggest why anaemia is a greater risk in multiple pregnancies?

The mother has to supply the nutrients to feed two (or more) babies; if she is not getting enough iron and folate in her diet, or through supplements, she will become anaemic.

Other complications include the following:

Pregnancy-related hypertensive disorders like pre-eclampsia and eclampsia are more common in twin pregnancies.
Pressure symptoms may occur in late pregnancy due to the increased weight and size of the uterus.
Labour often occurs spontaneously before term, with p remature delivery or premature rupture of membranes (PROM) .
Respiratory deficit ( shortness of breath, because of fast growing uterus) is another common problem.

Twin babies may be small in comparison to their gestational age and more prone to the complications associated with low birth weight (increased vulnerability to infection, losing heat, difficulty breastfeeding).

You will learn about low birth weight babies in detail in the Postnatal Care Module.

Malpresentation is more common in twin pregnancies, and they may also be ‘locked’ at the neck with one twin in the vertex presentation and the other in breech. The risks associated with malpresentations already described also apply: prolapsed cord, poor uterine contraction, prolonged or obstructed labour, postpartum haemorrhage, and fetal hypoxia and death.
Conjoined twins (fused twins, joined at the head, chest, or abdomen, or through the back) may also rarely occur.

8.8 Management of women with malpresentation or multiple pregnancy

As you have seen in this study session, any presentation other than vertex has its own dangers for the mother and baby. For this reason, all women who develop abnormal presentation or multiple pregnancy should ideally have skilled care by senior health professionals in a health facility where there is a comprehensive emergency obstetric service. Early detection and referral of a woman in any of these situations can save her life and that of her baby.

What can you do to reduce the risks arising from malpresentation or multiple pregnancy in women in your care?

During focused antenatal care of the pregnant women in your community, at every visit after 36 weeks of gestation you should check for the presence of abnormal fetal presentation. If you detect abnormal presentation or multiple pregnancy, you should refer the woman before the onset of labour.

Summary of Study Session 8

In Study Session 8, you learned that:

During early pregnancy, babies are naturally in the breech position, but in 95% of cases they spontaneously reverse into the vertex presentation before labour begins.
Malpresentation or malposition of the fetus at full term increases the risk of obstructed labour and other birth complications.
Common causes of malpresentations/malpositions include: excess amniotic fluid, abnormal shape and size of the pelvis; uterine tumour; placenta praevia; slackness of uterine muscles (after many previous pregnancies); or multiple pregnancy.
Common complications include: premature rupture of membranes, premature labour, prolonged/obstructed labour; ruptured uterus; postpartum haemorrhage; fetal and maternal distress which may lead to death.
Vertex malposition is when the fetal head is in the occipito-posterior position — i.e. the back of the fetal skull is towards the mother’s back instead of pointing towards the front of the mother’s pelvis. 90% of vertex malpositions rotate and deliver normally.
Breech presentation (complete, frank or footling) is when the baby’s buttocks present during labour. It occurs in 3–4% of labours after 34 weeks of pregnancy and may lead to obstructed labour, cord prolapse, hypoxia, premature separation of the placenta, birth injury to the baby or to the birth canal.
Face presentation is when the fetal head is bent so far backwards that the face presents during labour. It occurs in about 1 in 500 full term labours. ‘Chin posterior’ face presentations usually rotate spontaneously to the ‘chin anterior’ position and deliver normally. If rotation does not occur, a caesarean delivery is likely to be necessary.
Brow presentation is when the baby’s forehead is the presenting part. It occurs in about 1 in 1000 full term labours and is difficult to detect before the onset of labour. Caesarean delivery is likely to be necessary.
Shoulder presentation occurs when the fetal lie during labour is transverse. Once labour is well progressed, vaginal examination may feel the baby’s ribs, and an arm may sometimes prolapse. Caesarean delivery is always required unless a doctor or midwife can turn the baby head-down.
Multiple pregnancies are always at high risk of malpresentation. Mothers need greater antenatal care, and twins are more prone to complications associated with low birth weight and prematurity.
Any presentation other than vertex after 34 weeks of gestation is considered as high risk to the mother and to her baby. Do not attempt to turn a malpresenting or malpositioned baby! Refer the mother for emergency obstetric care.

Self-Assessment Questions (SAQs) for Study Session 8

Now that you have completed this study session, you can assess how well you have achieved its Learning Outcomes by answering the following questions. Write your answers in your Study Diary and discuss them with your Tutor at the next Study Support Meeting. You can check your answers with the Notes on the Self-Assessment Questions at the end of this Module.

SAQ 8.1 (tests Learning Outcomes 8.1, 8.2 and 8.4)

Which of the following definitions are true and which are false? Write down the correct definition for any which you think are false.

A Fundus — the ‘rounded top’ and widest cavity of the uterus.

B Complete breech — where the legs are bent at both hips and knee joints and are folded underneath the baby.

C Frank breech — where the breech is so difficult to treat that you have to be very frank and open with the mother about the difficulties she will face in the birth.

D Footling breech — when one or both legs are extended so that the baby presents ‘foot first’.

E Hypoxia — the baby gets too much oxygen.

F Multiple pregnancy — when a mother has had many babies previously.

G Monozygotic twins — develop from a single fertilised ovum (the zygote). They can be different sexes but they share the same placenta.

H Dizygotic twins — develop from two zygotes. They have separate placentas, and can be of the same sex or different sexes.

A is true. The fundus is the ‘rounded top’ and widest cavity of the uterus.

B is true. Complete breech is where the legs are bent at both hips and knee joints and are folded underneath the baby.

C is false . A frank breech is the most common type of breech presentation and is when the baby’s legs point straight upwards (see Figure 8.4).

D is true. A footling breech is when one or both legs are extended so that the baby presents ‘foot first’.

E is false . Hypoxia is when the baby is deprived of oxygen and risks permanent brain damage or death.

F is false. Multiple pregnancy is when there is more than one fetus in the uterus.

G is false. Monozygotic twins develop from a single fertilised ovum (the zygote), and they are always the same sex , as well as sharing the same placenta.

H is true. Dizygotic twins develop from two zygotes, have separate placentas, and can be of the same or different sexes.

SAQ 8.2 (tests Learning Outcomes 8.1 and 8.2)

What are the main differences between normal and abnormal fetal presentations? Use the correct medical terms in bold in your explanation.

In a normal presentation, the vertex (the highest part of the fetal head) arrives first at the mother’s pelvic brim, with the occiput (the back of the baby’s skull) pointing towards the front of the mother’s pelvis (the pubic symphysis ).

Abnormal presentations are when there is either a vertex malposition (the occiput of the fetal skull points towards the mother’s back instead towards of the pubic symphysis), or a malpresentation (when anything other than the vertex is presenting): e.g. breech presentation (buttocks first); face presentation (face first); brow presentation (forehead first); and shoulder presentation (transverse fetal).

SAQ 8.3 (tests Learning Outcomes 8.3 and 8.5)

a. List the common complications of malpresentations or malposition of the fetus at full term.
b. What action should you take if you identify that the fetus is presenting abnormally and labour has not yet begun?
c. What should you not attempt to do?
a. The common complications of malpresentation or malposition of the fetus at full term include: premature rupture of membranes, premature labour, prolonged/obstructed labour; ruptured uterus; postpartum haemorrhage; fetal and maternal distress which may lead to death.
b. You should refer the mother to a higher health facility – she may need emergency obstetric care.
c. You should not attempt to turn the baby by hand. This should only be attempted by a specially trained doctor or midwife and should only be done at a health facility.

SAQ 8.4 (tests Learning Outcomes 8.4 and 8.5)

A pregnant woman moves into your village who is already at 37 weeks gestation. You haven’t seen her before. She tells you that she gave birth to twins three years ago and wants to know if she is having twins again this time.

a. How would you check this?
b. If you diagnose twins, what would you do to reduce the risks during labour and delivery?
Is the uterus larger than expected for the period of gestation?
What is its shape – is it round (indicative of twins) or heart-shaped (as in a singleton pregnancy)?
Can you feel more than one head?
Can you hear two fetal heartbeats (two people listening at the same time) with at least 10 beats difference?
If there is access to a higher health facility, and you are still not sure, try and get the woman to it for an ultrasound scan.
Be extra careful to check that the mother is not anaemic.
Encourage her to rest and put her feet up to reduce the risk of increased blood pressure or swelling in her legs and feet.
Be alert to the increased risk of pre-eclampsia.
Expect her to go into labour before term, and be ready to get her to the health facility before she goes into labour, going with her if at all possible.
Get in early touch with that health facility to warn them to expect a referral from you.
Make sure that transport is ready to take her to a health facility when needed.

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pregnancy health center / pregnancy a-z list / what are the different fetal positions article

What Are the Different Fetal Positions?

Medical Author: Karthik Kumar, MBBS
Medical Reviewer: Pallavi Suyog Uttekar, MD

5 Types of Fetal Positions and Presentations

Comments **COMMENTSTAGLIST**
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The relationship between your baby's backbone and your backbone when your baby is in-utero is called the fetal position. Your baby can be in a variety of fetal positions, some make birth easier than others.

Longitudinal position: The fetus’ and mother’s backbones are parallel to each other in this position.
Transverse position: In this posture, the fetus’ backbone is at a right angle to the mother's backbone.
Oblique position: The inclination angle of the fetus backbone is more than 0 and less than 90 degrees of the mother's backbone in this position.

Most people, however, confuse fetal position with the fetal presentation.

Fetal position refers to whether the fetus is facing backward (facing the woman's back when she lies down) or forward (facing the woman's abdomen when she lies down).
Fetal presentation is the body part of the baby that leads the way out of the birth canal.

The fetal position and presentation of your baby may influence the difficulty of your delivery. The baby may drop down into the pelvis before the due date. Here are some of the different positions and presentations your baby can get into while you are preparing for childbirth .

During pregnancy and when preparing for childbirth , there are exercises moms can do when the baby is active to get it in the optimal fetal position, which is known as baby spinning. Starting at the 35th week of pregnancy, talk to your doctor about maternal positioning.

Occiput anterior (OA) or vertex presentation

This is the optimal fetal positioning for childbirth . The baby enters the pelvis with their head down and chin tucked to the chest, facing the mother's back. The head points to the birth canal in this position.

There are two more presentations in OA:

The baby will remain in the OA position, but the face, rather than the head, will be pointing toward the birth canal.
This occurs when the chin is not tucked against the chest and instead points outward.
During a vaginal examination, the doctor can detect this position by feeling the baby's bony jaws and mouth.
In brow presentation, the baby will be in the OA position with their forehead pointing toward the birth canal. The doctor can feel the anterior fontanelle and the orbits of the forehead during the vaginal examination.
One arm lies along with the head, pointing toward the birth canal.
The arms may slide back during the delivery process, but if they do not, extra care must be taken to safely remove the baby.

Occiput posterior (OP)

The baby enters the pelvis with its head down but facing the mother's front or abdomen.
In general, approximately 10 to 34 percent of babies remain in the OP position during the first stage of labor before shifting to the optimal (OA) position.
However, some babies remain in this position, which can make labor difficult and necessitate an emergency Cesarean delivery.
This fetal position can cause labor to be prolonged, resulting in instrumental interventions, severe perineal tears, or Cesarean delivery.

The cephalic presentation or head-first positions are referred to as OA and OP.

Occiput transverse (OT)

In the womb, the baby is lying sideways, and if they do not turn to the optimal position in time for birth, a Cesarean delivery is required.
During a vaginal examination, the doctor may feel the shoulder, arm, elbow, or hand protruding into the vagina.
This baby position increases the risk of umbilical cord prolapse, which occurs when the umbilical cord protrudes before the baby.
Cord prolapse can occur in about one percent of babies in the transverse position, which is a medical emergency that necessitates an immediate Cesarean delivery.
In some cases, assisted delivery is performed by manually rotating the baby or using forceps or a vacuum to position the baby in the ideal position.

Umbilical cord presentation

During this time, the umbilical cord is the first to emerge from the birth canal.
The condition of the uterine membrane, however, distinguishes umbilical cord presentation from prolapse.
A cord presentation occurs when the umbilical cord enters the birth canal before the water breaks, whereas a cord prolapse occurs after the water breaks, necessitating an emergency Cesarean delivery.

Breech position

The infant is positioned with its buttocks directed toward the birth canal, resulting in the following types of breech positions:

The buttocks are pointing toward the birth canal, with the legs folded at the knees and the feet close to the buttocks.
In a vaginal delivery, this position increases the risk of an umbilical cord loop. Furthermore, the cord may pass through the cervix before the head, injuring the baby.
The buttocks are pointing toward the birth canal with the legs straight up and the feet reaching the head.
This can result in an umbilical cord loop, which can injure the baby during vaginal birth.
The baby's buttocks are pointing down, and one of their feet is pointing toward the birthing canal.
This can result in an umbilical cord prolapse, which can cut off the fetus' blood supply and oxygen supply.

A clinical examination of the abdomen, a vaginal examination, or an ultrasound examination is used to determine the position and presentation of the fetus during pregnancy.

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18-Week Ultrasound: A Glimpse at Anatomy and Organ Health

What an 18-Week Test Can Find
Signs of a Normal Ultrasound
Pregnancy Complications

An ultrasound, also called a sonogram , is a test that uses sound waves to create a picture of a developing fetus during pregnancy. An 18-week ultrasound is performed to look at fetal anatomy.

It’s generally considered the earliest time a healthcare provider can get a detailed view of organs, such as the heart, brain, stomach, kidneys, spine, and genitals. The sex of the fetus can also be determined at 18 weeks .

This article discusses what to expect during an 18-week ultrasound, signs of a normal scan, and what to do if your ultrasound reveals a complication.

skynesher/ Getty Images

Learning the Sex of the Fetus

Though many people wait until the 18-week ultrasound to find out the sex of their baby, studies show ultrasounds performed after 14 weeks are nearly 100% accurate at identifying the sex. There are also blood tests that can determine the fetus's sex early on in pregnancy.

Information From an 18-Week Ultrasound

Ultrasound technicians (sonographers) will view and measure various parts of the fetus to make sure it's growing and developing normally. They may take a look at the following:

Overall size : The tech will estimate the fetus's weight and length. At this time in the pregnancy, most fetuses should weigh about 9 ounces and be about 7.75 inches long.
Limbs : The fetus's arms, legs, fingers, and toes are viewed. The tech may measure some of the limbs.
Face : The fetus will be viewed to ensure proper formation of the facial features. This can help identify conditions such as a cleft palate .
Brain : The sonographer will examine and measure the fetus's skull and brain to look for rare problems, such as cysts, that could affect development.
Heart : The fetus's heart will be evaluated to count the chambers, analyze the blood flow, and check the heart rate.
Spine : Looking at the spine can help determine if the fetus's vertebrae are aligned and if skin is covering the spine at the back.
Kidneys and bladder : The tech should be able to see if the fetus's bladder is working correctly.
Sex organs : Your sonographer will examine the fetus's sex organs to look for abnormalities. They will also be able to determine the sex. You can let them know if you do not want to know this information.
Stomach : The tech will look for any defects in the abdomen.
Other measurements : The tech will examine the pregnant patient's uterus, ovaries, and cervix. They will also measure the blood flow in the umbilical cord and the amount of amniotic fluid . The exam will look for placenta previa, which occurs when the placenta lies too low in the uterus.

Stillbirth vs. Miscarriage on Ultrasound

A stillbirth happens when a fetus dies in the uterus after 20 weeks of pregnancy. If the fetus passes away before or at the 18-week ultrasound, it's known as a miscarriage .

Signs of Normal 18-Week Ultrasound

An 18-week ultrasound usually yields normal results. In a typical ultrasound at this time, normal fetal limb and organ development can be seen.

The technician will probably not tell you your results right away, however. They will share the images with your healthcare provider, who will then meet with you to discuss the results. However, you can find out the sex during the sonogram.

Waiting Until 20 Weeks for an Ultrasound

An anatomy scan can be done between 18 and 22 weeks of pregnancy. Some healthcare providers choose to wait until at least 20 weeks to perform the ultrasound.

Signs of Pregnancy Complications at an 18-Week Ultrasound

Some possible abnormalities that can be identified on an 18-week ultrasound include:

Limb issues : A missing or irregular finger, toe, leg, or arm may be spotted.
Spina bifida : This occurs when the fetus’s spinal cord doesn’t develop properly.
Cleft palate : This results when the fetus’s lip or mouth doesn’t form normally during pregnancy.
Anencephaly : This is a condition in which the fetus is missing parts of the skull and brain.
Bilateral renal agenesis : This condition happens when the fetus’s kidneys don’t develop.
Heart issues : Several types of heart defects can be identified on the scan.
Gastroschisis : This is an abdominal wall defect in which an opening forms near the belly button.
Omphalocele : This is an abdominal wall defect in which an opening forms in the belly button.
Skeletal dysplasia : This condition causes problems with development of the bones, joints, and cartilage.
Rare genetic conditions : These may include Edwards’ syndrome (trisomy 18) or Patau’s syndrome (trisomy 13).
Diaphragmatic hernia : A condition that causes an abnormal opening in the diaphragm, located below the lungs.
Irregular or slow growth : This means the fetus is not growing correctly.

A Word From Verywell

Although ultrasound can identify many things, some abnormalities can't be detected through that form of imaging. Screening tests during pregnancy usually mean that further evaluation or testing is needed.

Next Steps After an 18-Week Ultrasound

The 18-week ultrasound won't give you a formal diagnosis for any health condition. Instead, it lets you know that you may need more testing.

If your healthcare provider spots a possible abnormality or is concerned about any findings, they might recommend that you have another ultrasound with an expert who specializes in high-risk pregnancies. Or, they may suggest that you have an amniocentesis , a procedure in which a thin needle is inserted into the uterus to remove amniotic fluid, which is tested in a lab.

Your 18-week ultrasound is a scan that's performed about halfway through your pregnancy. It examines different organs in the fetus and pregnant person's body. You can also find out your baby's sex during the procedure.

Most of the time, scans come back with normal results. However, your ultrasound may reveal possible complications. If this happens, you might need to undergo more testing, or your healthcare provider may closely monitor your condition until delivery.

MedlinePlus. Ultrasound pregnancy .

Bethune, M., Alibrahim, E., Davies, B., & Yong, E. A pictorial guide for the second-trimester ultrasound . Australasian Journal of Ultrasound in Medicine , 16 (3), 98-113. doi:10.1002/j.2205-0140.2013.tb00106.x

Kearin M, Pollard K, Garbett I. Accuracy of sonographic fetal gender determination: predictions made by sonographers during routine obstetric ultrasound scans . Australas J Ultrasound Med . 2014;17(3):125-130. doi: 10.1002/j.2205-0140.2014.tb00028.x.

Novant Health. 18-20 week ultrasound: What your doctor is checking for .

UPMC Health. What happens during a 20-week anatomy scan .

Penn Medicine. All about the 20-week anatomy scan .

March of Dimes. Stillbirth .

NHS. 20-week screening scan .

UT Southwestern Medical Center. Amniocentesis and cvs: FAQs about the prenatal diagnostic duo .

By Julie Marks Marks is a Florida-based freelance health writer with a bachelor's degree in broadcast journalism and creative writing.

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Prenatal diagnosis of Freeman-Sheldon syndrome using ultrasound and genetic testing. Case report

Affiliations.

1 Universidad de Cartagena, Cartagena de Indias (Colombia). . [email protected].
2 Clínica de la Mujer Cartagena S.A.S., Cartagena de Indias (Colombia).. [email protected].
3 Centro Hospitalario Serena del Mar, Cartagena de Indias (Colombia).. [email protected].
PMID: 38421226
PMCID: PMC10911420
DOI: 10.18597/rcog.4019

Abstract in English, Spanish

Objectives: To describe a case of prenatal diagnosis of Freeman-Sheldon syndrome based on ultrasound findings and complete fetal exome sequencing.

Materials and methods: A 33-year-old patient currently on treatment for hypothyroidism in whom a 19-week detailed anatomical ultrasound scan showed fetal deformities in more than two body areas (upper and lower limbs), suggesting a diagnosis of arthrogryposis. Genetic counseling was provided and amniocentesis was performed at 20 weeks for fluorescence in situ hybridization (FISH) analysis and complete fetal exome sequencing, with the latter allowing the identification of a heterozygous pathogenic variant of the MYH3 gene which is associated with type 2A distal arthrogryposis.

Conclusions: Complete fetal exome sequencing was a key factor in identifying the MYH3 gene mutation and confirmed that the deformities seen on ultrasound were associated with type 2A distal arthrogryposis. It is important to perform complete fetal exome sequencing in cases of joint malformations seen on prenatal ultrasound.

Objetivos: describir un caso de diagnóstico prenatal de síndrome de Freeman-Sheldon mediante hallazgos ecográficos y secuenciación completa del exoma fetal.

Materiales y métodos: mujer de 33 años, con antecedentes de hipotiroidismo en tratamiento, a quien en semana 19 se realizó ecografía de detalle anatómico, en la cual se observaron deformidades en el feto en más de dos áreas corporales (extremidades superiores e inferiores), sugiriendo el diagnóstico de artrogriposis. Posteriormente, se brindó asesoría genética y se realizó amniocentesis en semana 20 de gestación, con análisis de la hibridación in situ por fluorescencia, seguido de secuenciación completa del exoma fetal. Este último examen permitió identificar una variante patogénica heterocigota en el gen MYH3, la cual se asocia con la artrogriposis distal tipo 2A.

Conclusiones: la realización de la secuenciación completa de exoma fetal es un factor clave para identificar la mutación del gen MYH3, y confirma que las deformidades evidenciadas por ultrasonido estaban relacionadas con la artrogriposis distal tipo 2A. Es importante hacer la secuenciación de exoma fetal en fetos que muestren hallazgos de malformaciones articulares en el ultrasonido prenatal.

Keywords: Arthrogryposis; club foot; exome; syndrome; prenatal diagnosis.

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Conflict of interest statement

Conflicto de intereses: los autores declaran no tener ningún conflicto de intereses.

Figura 1. Hallazgos de alteraciones anatómicas en…

Figura 1. Hallazgos de alteraciones anatómicas en ecografía de detalle anatómico 1A y 1B: exploración…

Figura 2. Imagen posnatal de extremidades en…

Figura 2. Imagen posnatal de extremidades en las que se evidencian alteraciones morfológicas en extremidades.…

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DOI: 10.1016/j.mric.2024.03.005
Corpus ID: 269371671

MR Imaging of the Fetal Gastrointestinal Anomalies.

E. Rubesova , Marine Moeremans
Published in Magnetic Resonance Imaging… 1 April 2024

37 References

Fetal bowel anomalies – us and mr assessment, magnetic resonance imaging of the fetal gastrointestinal system, fetal mr imaging of gastrointestinal abnormalities., does prenatal mri enhance fetal diagnosis of intra‐abdominal cysts, magnetic resonance imaging in the prenatal diagnosis of congenital diarrhea, fetal bowel dilatation: a sonographic sign of uncertain prognosis, three-dimensional mri volumetric measurements of the normal fetal colon., mri of fetal gi tract abnormalities, fetal enterolithiasis: prenatal sonographic and mri diagnosis in two cases of urorectal septum malformation (ursm) sequence, prenatal detection of esophageal atresia: a systematic review and meta‐analysis, related papers.

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IMAGES

Maternal-fetal US categories from our dataset: image examples, total
Fetal Presentation
Situs or sidedness: The first step in assessing the fetal heart
Routine first-trimester ultrasound screening using a standardized
images
fetal presentations & positions

VIDEO

Normal fetal heart ultrasound, color Doppler echocardiography, 4 chamber view
प्रेग्नेंसी में कितनी बार अल्ट्रासाउंड करवाना चाहिए/Ultrasoundin pregnancy /Dr ShikhaAgarwal
Fetal Ultrasound
pregnancy life
Fetal echocardiography ultrasound|Antenatal ultrasound|Fetal echocardiography ultrasound
What Are The Different Birth Positions ‖ Breech Presentation ‖ Fetal Position & Presentation

COMMENTS

Variation in fetal presentation
breech presentation: fetal rump presenting towards the internal cervical os, this has three main types. frank breech presentation (50-70% of all breech presentation): hips flexed, knees extended (pike position) complete breech presentation (5-10%): hips flexed, knees flexed (cannonball position) footling presentation or incomplete (10-30%): one ...
Fetal Positions For Birth: Presentation, Types & Function
Possible fetal positions can include: Occiput or cephalic anterior: This is the best fetal position for childbirth. It means the fetus is head down, facing the birth parent's spine (facing backward). Its chin is tucked towards its chest. The fetus will also be slightly off-center, with the back of its head facing the right or left.
Fetal Presentation, Position, and Lie (Including Breech Presentation)
Fetal lie: Relation of the fetus to the long axis of the uterus; longitudinal, oblique, or transverse. Normal fetal lie is longitudinal, normal presentation is vertex, and occiput anterior is the most common position. Abnormal fetal lie, presentation, or position may occur with. Fetopelvic disproportion (fetus too large for the pelvic inlet)
Fetal presentation before birth
Frank breech. When a baby's feet or buttocks are in place to come out first during birth, it's called a breech presentation. This happens in about 3% to 4% of babies close to the time of birth. The baby shown below is in a frank breech presentation. That's when the knees aren't bent, and the feet are close to the baby's head.
Fetal Presentation, Position, and Lie (Including Breech Presentation)
If the fetus is in a different position, lie, or presentation, labor may be more difficult, and a normal vaginal delivery may not be possible. Variations in fetal presentation, position, or lie may occur when. The fetus is too large for the mother's pelvis (fetopelvic disproportion). The uterus is abnormally shaped or contains growths such as ...
Delivery, Face and Brow Presentation
The term presentation describes the leading part of the fetus or the anatomical structure closest to the maternal pelvic inlet during labor. The presentation can roughly be divided into the following classifications: cephalic, breech, shoulder, and compound. Cephalic presentation is the most common and can be further subclassified as vertex, sinciput, brow, face, and chin. The most common ...
Ultrasound determination of fetal lie and presentation
The fetal presentation describes the fetal part that is lowest in the maternal abdomen. In case of labor, it is the lowest fetal part in the birth canal. Many fetal presentations are possible: Cephalic presentation: the fetal head is the lowest fetal part. This is by far the most common presentation at term of pregnancy and in labor.
Fetal presentation: Breech, posterior, transverse lie, and more
Fetal presentation and position During the last trimester of your pregnancy, your provider will check your baby's presentation by feeling your belly to locate the head, bottom, and back. If it's unclear, your provider may do an ultrasound or an internal exam to feel what part of the baby is in your pelvis.
Breech Presentation
Breech presentation refers to the fetus in the longitudinal lie with the buttocks or lower extremity entering the pelvis first. The three types of breech presentation include frank breech, complete breech, and incomplete breech. In a frank breech, the fetus has flexion of both hips, and the legs are straight with the feet near the fetal face, in a pike position.
Sonography Fetal Assessment, Protocols, and Interpretation
Fetal ultrasonography is a standard and vital component of a comprehensive fetal evaluation in pregnancy. There are specific indications for using ultrasound in each trimester and assessing both the fetus and the mother by ultrasonography. Based on maternal and fetal risk factors, ultrasound timing and frequency are individualized to evaluate ...
Ultrasound determination of fetal lie and presentation
Cephalic presentation: the fetal head is the lowest fetal part. This is by far the most common presentation at term of pregnancy and in labor. Breech: the fetal buttock or feet are the lowest fetal part. Shoulder: the fetal shoulder is the lowest fetal part. Compound: a combination of more than one fetal structure lies closest to the pelvic inlet.
Cephalic Position: Understanding Your Baby's Presentation at Birth
Cephalic occiput anterior. Your baby is head down and facing your back. Almost 95 percent of babies in the head-first position face this way. This position is considered to be the best for ...
Understanding Fetal Position
The best fetal position for your baby to be shortly before birth is feet up, head down, facing your back, with their back resting against your belly. This means that they can exit the birth canal ...
Fetal Ultrasound > Fact Sheets > Yale Medicine
Ultrasound is the most widely used medical imaging method for viewing a fetus during pregnancy. It is also utilized to guide procedures such as amniocentesis or chorionic villus sampling . An ultrasound may be done at almost any time during a pregnancy, even as early as about five weeks after conception. During the first trimester, it can ...
PDF Stepwise Standardized Approach to The Basic Obstetric 10 Ultrasound
Chapter 10: Stepwise Standardized Approach to the Basic Obstetric Ultrasound Examination in the Second and Third Trimester 188 presence of a fetal head on the ultrasound monitor confirms a cephalic presentation Figure ( 10.4) and the presence of fetal buttocks confirms a breech presentation (Figure 10.5).Note that
Abnormal Presentation
Compound presentation means that a fetal hand is coming out with the fetal head. This is a problem because: The amount of baby that must come through the birth canal at one time is increased. There is increased risk of mechanical injury to the arm and shoulder, including fractures, nerve injuries and soft tissue injury.
The evolution of fetal presentation during pregnancy: a retrospective
We investigated changes in the frequencies of four primary types of singleton fetal lie/presentation for each gestational week from 18 to 39 weeks in a retrospective, cross-sectional study which analyzed ultrasound examination records of fetal positions, in the outpatient prenatal diagnosis clinics in two cities in Poland.
PDF Malpresentations, Malpositions, and Multiple Gestation
presentation, the reference point is the sacrum and the desired position during delivery is sacrum anterior. Methods of Diagnosis There are three principal methods of determining fetal lie, presentation, and position: (1) Leopold maneuvers, or abdominal palpation, (2) vaginal examination, and (3) imaging with ultrasound. Ultrasound examination
Labour and Delivery Care Module: 8. Abnormal Presentations ...
8.1 Normal and abnormal presentations 8.1.1 Vertex presentation. In about 95% of deliveries, the part of the fetus which arrives first at the mother's pelvic brim is the highest part of the fetal head, which is called the vertex (Figure 8.1).This presentation is called the vertex presentation.Notice that the baby's chin is tucked down towards its chest, so that the vertex is the leading ...
Sonographic evaluation of the fetal head position and attitude during
Fetal malpresentation, malposition, and asynclitism are among the most common determinants of a protracted active phase of labor, arrest of dilatation during the first stage, and arrest of descent in the second stage. The diagnosis of these conditions is traditionally based on vaginal examination, which is subjective and poorly reproducible. Intrapartum sonography has been demonstrated to ...
What Are the Different Fetal Positions?
The different fetal positions include occiput anterior position (OA), occiput posterior (OP) position, occiput transverse (OT) position, and 3 types of breech positions. The relationship between your baby's backbone and your backbone when your baby is in-utero is called the fetal position. Your baby can be in a variety of fetal positions, some ...
PDF Doppler Ultrasound
Doppler ultrasound in general and obstetric ultrasound scanners uses pulsed wave ultrasound (Figure 4). This allows measurement of the depth (or range) of the flow site. Additionally, the size of the sample volume (or range gate) can be changed. Pulsed wave ultrasound is used to provide data for Doppler sonograms and color flow images.
PDF PowerPoint Presentation
Presents in 0.004% of all pregnancies. Arrested development of bronchial. tree. Ultrasound is useful to identify: ‐ Anatomical location. ‐ Its relationship with the bronchial tree. ‐ Size and number of cysts. ‐ Identification of any coexisting BPS. Fetal Thorax.
PDF Competency Workbook Ultrasound Examination for Fetal Presentation
Dimension 3: ultrasound examination. Prior to ultrasound examination. ationSpecify to parents the limitations of a. presentation scanPrepare the working area and the scan mach. e. Turn on the scan machine following the appropriate proce. re.Ensure transducers and cables are fixed s.
18-Week Ultrasound: Anatomy Reveal and Insights
An 18-week ultrasound is sometimes called a fetal anatomy scan. You could learn the sex of the fetus. Learn about normal and abnormal results. ... Heart issues: Several types of heart defects can be identified on the scan. Gastroschisis: This is an abdominal wall defect in which an opening forms near the belly button.
Prenatal diagnosis of Freeman-Sheldon syndrome using ultrasound and
Objectives: To describe a case of prenatal diagnosis of Freeman-Sheldon syndrome based on ultrasound findings and complete fetal exome sequencing. Materials and methods: A 33-year-old patient currently on treatment for hypothyroidism in whom a 19-week detailed anatomical ultrasound scan showed fetal deformities in more than two body areas (upper and lower limbs), suggesting a diagnosis of ...
MR Imaging of the Fetal Gastrointestinal Anomalies
The normal appearance of the fetal bowel on US and MRI as well as the typical presentations of bowel pathologies are reviewed and the importance of recognizing on fetal MRI the abnormalities of size and T1-weighted signal of the meconium-filled distal bowel is discussed. Expand

Variation in fetal presentation

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Fetal Presentation, Position, and Lie (Including Breech Presentation)

Position and Presentation of the Fetus

Variations in Fetal Position and Presentation

Occiput posterior position

Breech presentation

Other presentations

Breech, posterior, transverse lie: What position is my baby in?

Fetal presentation and position

Head down, facing down (anterior position)

Head down, facing up (posterior position)

Frank breech

Complete breech

Incomplete breech

Single footling breech

Double footling breech

Transverse lie

Oblique lie

What to know if your baby is breech

9 of the most jaw-dropping breech birth photos

What's a sunny-side up baby?

Raspberry leaf tea is popular during pregnancy – but possible benefits aren't proven

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Fetal Ultrasound

What is ultrasound?

Labour and Delivery Care Module: 8. Abnormal Presentations and Multiple Pregnancies

Learning Outcomes for Study Session 8

8.1 Normal and abnormal presentations

8.1.2 Malpresentations

8.1.3 Malposition

8.2 Causes and consequences of malpresentations and malpositions

8.3 Breech presentation

8.3.1 Causes of breech presentation

8.3.2 Diagnosis of breech presentation

8.3.3 Types of breech presentation

8.3.4 Risks of breech presentation

8.4 Face presentation

8.4.1 Causes of face presentation

8.4.2 Diagnosis of face presentation

8.4.3 Complications of face presentation

8.5 Brow presentation

8.5.1 Possible causes of brow presentation

8.5.2 Diagnosis of brow presentation

8.5.3 Complications of brow presentation

8.6 Shoulder presentation

8.6.1 Causes of shoulder presentation

8.6.2 Diagnosis of shoulder presentation

8.6.3 Complications of shoulder presentation

8.7 Multiple pregnancy

8.7.1 Types of twin pregnancy

8.7.2 Diagnosis of twin pregnancy

8.7.3 Consequences of twin pregnancy

8.8 Management of women with malpresentation or multiple pregnancy

Summary of Study Session 8

Self-Assessment Questions (SAQs) for Study Session 8

SAQ 8.1 (tests Learning Outcomes 8.1, 8.2 and 8.4)

SAQ 8.2 (tests Learning Outcomes 8.1 and 8.2)

SAQ 8.3 (tests Learning Outcomes 8.3 and 8.5)

SAQ 8.4 (tests Learning Outcomes 8.4 and 8.5)

What Are the Different Fetal Positions?

5 Types of Fetal Positions and Presentations